For example, a power conversion device used as a power conditioner for photovoltaic generation converts a DC generated power to an AC power, to perform power interconnection to a commercial power grid. In a traditional power conversion device, a boost converter steps up a generated voltage to a certain voltage higher than a peak voltage on the AC side, and then an inverter circuit converts the voltage to an AC voltage. In this case, the boost converter and the inverter circuit always perform high-speed switching operations. Meanwhile, in such a power conversion device, it is important to improve the conversion efficiency. Accordingly, the following control is proposed: while the voltage on the DC side and the instantaneous voltage on the AC side are always compared with each other, the boost converter is caused to perform switching operation only during a period in which step-up operation is needed, and the inverter circuit is caused to perform switching operation only during a step-down operation is needed (see, for example, Patent Literature 1, 2). If the period in which the switching operation is stopped is provided to the boost converter and the inverter circuit owing to the above control, switching loss and the like are reduced by the amounts corresponding to the stop period, leading to improvement in the conversion efficiency.